19:12 <+Eggsalad> renesis: You is a computer program, and i find your holes i'm going to back your ass it worth two in the top of the deflector shield in space.
arcturus`: he can prob right into the pic
*wire right into

thats why i says maybe
i would laugh if you cracked it open and it was an atmel mcu
usually its the people who come in
and go like I CAN DO THIS OR THIS OR THIS OR THIS OR THIS OR THIS
WHAT DO I DO
those people have more of a chance
its either trs or trss
the audio cable
er trrs
anyway open it up take pics

like, you sensor could be at just under max ref voltage, with a periodic noise spike of 1/2 the max ref
and it wouldnt see the top half and the average during the spike would end up like 25% low (guessing)

near an electric ignition gas engine
yeah thats just bad noise
so use some TVS devices on the inputs
MOVs and fat schottky diodes
depending on sensor they may have to be low leakage devices
anyway this is how i would do adc on anything that really mattered
you can always filter in the uC but if it clips out your ref because of noise its going to make the sensor reading off
you wont get even distribution of noise voltage above and below your signal voltage so the average wont be accurate

and the digital stuff
then decide how much latency is acceptable in your measurement
i would factor in processing times in the microcontroller, but i dunno maybe thats not even significant
then do a filter on the input of the amplifier tuned to as low a freq as possible without creating unallowable latency
you prob want multiple poles, this could be active or passive, and you prob want it tuned towards DC to be effective (~1Hz)
but thats maybe too much latency, but say something like thermal sense, thats prob fine
this will help eliminate the noise from outside device
yeah in a car

star ground everything at the psu supply caps
awesome
so put youre biggest psu caps at the bus connector
*your
and then just star ground different systems
also instead of a lower reference, i would use something like a 4.096V precision voltage ref (1 LSB = 4mV)
and then use a low input voltage offset rail to rail opamp to scale your max input signal to like 4.0V
that will help you get above the noise inside your device, from the psu and the can bus

it doesnt matter so much if you have common power supplies
something could blow up the ic and glitch the psu which could take out the running system on the other side
yeah but you wont be able to measure it well through an opto if you need absolute analog voltage readings
maybe parts exist that are precise enough, or you could design a system you could calibrate (would need to test that in all sorts of situations) but thats not something ive ever tried to do
you could explore analog/digital system ground techniques
like isolated grounds connected through combinations of resistors, caps and coils
or you can just ground everything well